function _new(fn, ...args) {
  var obj = Object.create(fn.prototype)
  var result = fn.apply(obj, args)
  return typeof result === 'object' ? result : obj
}
function Person(name, age, gender) {
  this.name = name
  this.age = age
  this.gender = gender
}
console.log(_new(Person, 'xjt', 20, 'male'))